Jump to content

Bad noise on SID output


marioguzzi
 Share

Recommended Posts

Hi all,

after solving the DIN problem I started building the second SID module for my synth.

1 Core r4d

1 Sid r3d (with 8580chip) and 2200uF electrolytic cap

optimized c64 psu

Due to some soldering paste left on the board when I connected the board to test voltages I got some smoke and sparkles between the voltage regulator and c10(330nF). I cleaned the board and replaced them.

Voltages on SID module are 8,9V at the voltage regulator output and 5,15V from Core module

Now, I'm getting a lot of noise, with or without the 8580.

Probably something got fried during the first test, but I don't know which components to check, any help appreciated ???

Here's a snapshot of scope and spectrum taken WITHOUT the 8580 chip

EDIT: oh, don't look for stereo snapshot, as only the problematic SID module is connected to the oscilloscope

20071229181920_noise.JPG

Link to comment
Share on other sites

Wow, that's a nice spectrum of something between white and pink noise!

A question that comes to mind is: how loud is the noise? If there's a broken connection in the audio-path and you crank up the volume you can always generate noise of this type, but if this noise is really loud (the same loudness of a SID output) then something else is actively producing this noise. A couple of things come to mind:

- Check if the problem isn't coming from a dirty power rail. If something got damaged due to the sparks and smoke you should be able to see this with your scope. An unstable power supply could cause this noise.

- Transistor T1 could be damaged due to voltage peaks when the sparks and smoke were going on

- Transistor T1 could be pin swapped

Greetings,

Rutger

Link to comment
Share on other sites

thanks for the replies!

swapping the chips has no positive effects, and anyway the noise is present even without the chip (and really loud) so I can exclude that the problem is related to the chip.

I'd exclude also problems related to power supply, in fact with the other SID module the noise I get is much lower, i.e. volume not comparable to SID output.

I'll let you know once I replace T1

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...